Name: analysis of chromosome segregation, histone acetylation, and spindle morphology in horse oocytes
Uploaded: 2017-05-11T14:00:00
Description: Watch this Scientific Journal Video about Analysis of Chromosome Segregation, Histone Acetylation, and Spindle Morphology in Horse Oocytes at JoVE.com

The authors would like to thank Fabrice Vincent for the support with laser scanning confocal microscopy (LSCM), and Philippe Barri&#232;re and Thierry Blard for performing daily ultrasound ovarian scanning and hCG injection. This work was supported in part by the &#34;Regione Sardegna and Regione Lombardia&#34; project &#34;Ex Ovo Omnia&#34; (Grant no. 26096200 to A. M. L.); the &#34;L&#39;Oreal Italia per le Donne e la Scienza 2012&#34; fellowship (Contract 2012 to F. F.), FP7-PEOPLE-2011- CIG, Research Executive Agency (REA) &#34;Pro-Ovum&#34; (Grant no. 303640 to V. L.); and by the Postdoctoral School of Agriculture and Veterinary Medicine, co-financed by the European Social Fund, Sectorial Operational Program for Human Resource Development 2007-2013 (Contract no. POSDRU/89/1.5/S/62371 to I. M.). The in vivo oocyte collection was financed by the Institut Fran&#231;ais du Cheval et de l&#39;Equitation.

All the procedures were approved by the Animal Care and Use Committee CEEA Val de Loire Number 19 and were performed in accordance with the Guiding Principles for the Care and Use of Laboratory Animals.
1. Oocyte Collection and In Vitro Maturation
<ol>
	<li>Ovum pick-up
	<ol>
		<li>Daily assess by ultrasound the diameter of ovarian follicles in a cohort of adult mares. At the emergence of a follicle &#8805;33 mm (dominant follicle), inject the mare with 1,500 IU of ...

<ol>
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Even though IVM has been performed in horses for more than 20 years16, we do not yet know whether the oocyte can be the origin of embryonic aneuploidy, as has been proposed for humans17. The reason is probably that the preparation of oocyte spreads for chromosome counting results in considerable sample loss. With this in mind, a survey of the methods used for investigating errors in chromosome segregation was conducted to search for the most appropriate technique to apply t...

A vast array of assisted reproduction techniques has been developed to treat infertility in women, companion animals, and endangered species. One of the most common procedures in clinical settings is the retrieval of metaphase II (MII)-stage oocytes from the ovarian follicles by ultrasound-guided transvaginal aspiration, ovum pick-up (OPU)1. These oocytes are then fertilized in vitro (IVF), with the resulting embryo(s) implanted in a recipient uterus. The MII-stage (mature) oocytes are retrieved following the administration of exogenous gonadotropins. However, this treatment is associated, in some patients, with the development of ovarian hyperstimulation syndrome (OHSS)2.
Taking advantage of the intrinsic ability of fully-grown, immature oocytes (GV-stage) to spontaneously resume meiosis once isolated from their follicles, it is possible to obtain mature oocytes without administering gonadotropin3. This procedure is called oocyte in vitro maturation (IVM) and represents a less drug-oriented, less expensive, and more patient-friendly approach to assisted reproductive technology. However, the success of embryo development with in vitro-matured oocytes is generally lower than with in vivo matured oocytes4,5. A possible explanation is that in vitro matured oocytes are more affected by errors in chromosome segregation, and the resulting aneuploidy impairs normal embryonic development6.
Understanding the molecular basis of chromosomal mis-segregation during IVM would ultimately disclose the full potential of this technique. In this vein, the experimental approach used to investigate the morphological and biochemical features of in vitro-matured oocytes, compared to in vivo matured oocytes is here described7,8. Specifically, the procedures for the OPU of immature and mature oocytes and the IVM of immature oocytes are illustrated using adult and naturally-cycling horses as an experimental model. Then, immunofluorescence and image analysis are used to investigate chromosome segregation, spindle morphology, and the global pattern of histone acetylation on these gametes. Finally, a protocol of reverse-transcription and quantitative PCR is described for the analysis of mRNA expression.
Compared with rodent animal models, horses do not allow genetic manipulation, are less easy to manipulate, and require expensive maintenance. However, this model is gaining considerable interest for the study of oocyte maturation9,10 due to the similarity to human ovarian physiology11,12. Moreover, the development of reliable protocols of IVM-IVF in the horse has a substantial economic interest, as it would allow for an increase in the number of foals from mares of high genetic value.
One of the limitations of performing experiments on oocytes, especially in monovulatory species, is the restricted sample availability. This limit has been overcome here by adjusting an approach, previously developed in mice, to horse oocytes13,14 in order to conduct chromosome counting that minimizes the sample loss (see the discussion for a comparison with other available techniques). Moreover, a triple-fluorescence staining protocol has been optimized to conduct multiple analyses on the same sample, and q-PCR analyses were performed on pools of 2 oocytes only.
Overall, the present study describes an experimental approach aimed to morphologically and biochemically characterize the horse oocyte, a cell type that is extremely challenging to study due to the low sample availability. However, it can expand our knowledge of the reproductive biology and infertility of monovulatory species.

<table border="0" cellpadding="0" cellspacing="0" width="802">
	<tbody>
		<tr height="21">
			<td height="21" style="height:21px;width:369px;">ultrasound probe</td>
			<td style="width:159px;">Aloka</td>
			<td style="width:113px;">UST-5820-7,5</td>
			<td style="width:161px;"></td>
		</tr>
		<tr height="21">
			<td height="21" style="height:21px;">human chorionic gonadotrophin&#160;</td>
			<td>centravet</td>
			<td>CHO004</td>
			<td>1500unit/animal IV</td>
		</tr>
		<tr height="21">
			<td height="21" style="height:21px;">detomidine</td>
			<td>centravet</td>
			<td>MED010</td>
			<td>9-15&#181;g/kg IV</td>
		</tr>
		<tr height="21">
			<td height="21" style="height:21px;">butylscopolamine bromure&#160;</td>
			<td>centravet</td>
			<td>EST001</td>
			<td>0,2mg/kg IV</td>
		</tr>
		<tr height="21">
			<td height="21" style="height:21px;">stereomicroscope</td>
			<td style="width:159px;">NIKON</td>
			<td style="width:113px;">SMZ-2B</td>
			<td></td>
		</tr>
		<tr height="21">
			<td height="21" style="height:21px;">butorphanol</td>
			<td>centravet</td>
			<td>DOL003</td>
			<td>10&#181;g/kg IV</td>
		</tr>
		<tr height="21">
			<td height="21" style="height:21px;">benzyl-penicillin</td>
			<td>centravet</td>
			<td>DEP203 IM</td>
			<td>15000UI/animal</td>
		</tr>
		<tr height="21">
			<td height="21" style="height:21px;">TCM199</td>
			<td>Sigma-Aldrich</td>
			<td>M3769 10X1L</td>
			<td>powder for hepes-buffered TCM199</td>
		</tr>
		<tr height="21">
			<td height="21" style="height:21px;">Hepes sodium salt</td>
			<td>Sigma-Aldrich</td>
			<td>H3784-100G</td>
			<td></td>
		</tr>
		<tr height="21">
			<td height="21" style="height:21px;">bovine serum albumin</td>
			<td>Sigma-Aldrich</td>
			<td>A8806</td>
			<td></td>
		</tr>
		<tr height="21">
			<td height="21" style="height:21px;">heparin&#160;</td>
			<td>Sigma-Aldrich</td>
			<td>H3149-10KU</td>
			<td></td>
		</tr>
		<tr height="25">
			<td height="25" style="height:25px;">NaHCO3-buffered TCM199</td>
			<td>Sigma-Aldrich</td>
			<td>M2154-500ML</td>
			<td>liquid for IVM medium</td>
		</tr>
		<tr height="21">
			<td height="21" style="height:21px;">epidermal growth factor</td>
			<td>Sigma-Aldrich</td>
			<td>E4127</td>
			<td></td>
		</tr>
		<tr height="21">
			<td height="21" style="height:21px;">newborn calf serum</td>
			<td>Sigma-Aldrich</td>
			<td>N4762-500ML</td>
			<td></td>
		</tr>
		<tr height="21">
			<td height="21" style="height:21px;">4-well dishes</td>
			<td>NUNCLON</td>
			<td>144444</td>
			<td></td>
		</tr>
		<tr height="21">
			<td height="21" style="height:21px;">incubator</td>
			<td>Heraeus</td>
			<td>BB6060</td>
			<td></td>
		</tr>
		<tr height="21">
			<td height="21" style="height:21px;">monastrol</td>
			<td>Sigma-Aldrich</td>
			<td>M8515</td>
			<td></td>
		</tr>
		<tr height="21">
			<td height="21" style="height:21px;">hyaluronidase</td>
			<td>Sigma-Aldrich</td>
			<td>H3506</td>
			<td></td>
		</tr>
		<tr height="21">
			<td height="21" style="height:21px;">pronase</td>
			<td>Sigma-Aldrich</td>
			<td>P5147</td>
			<td></td>
		</tr>
		<tr height="21">
			<td height="21" style="height:21px;">paraformaldehyde</td>
			<td>Sigma-Aldrich</td>
			<td>P6148</td>
			<td></td>
		</tr>
		<tr height="21">
			<td height="21" style="height:21px;">polyvinyl alcohol</td>
			<td>Sigma-Aldrich</td>
			<td>341584</td>
			<td></td>
		</tr>
		<tr height="21">
			<td height="21" style="height:21px;">triton-X 100</td>
			<td>Sigma-Aldrich</td>
			<td>T8787</td>
			<td></td>
		</tr>
		<tr height="21">
			<td height="21" style="height:21px;">normal donkey serum&#160;</td>
			<td>Sigma-Aldrich</td>
			<td>D9663</td>
			<td></td>
		</tr>
		<tr height="21">
			<td height="21" style="height:21px;">rabbit anti-Aurora B phospho-Thr232&#160;</td>
			<td>BioLegend</td>
			<td>636102</td>
			<td></td>
		</tr>
		<tr height="21">
			<td height="21" style="height:21px;">TRITC-conjugated donkey anti-rabbit IgG&#160;</td>
			<td>Vector Laboratories</td>
			<td>711-025-152</td>
			<td></td>
		</tr>
		<tr height="21">
			<td height="21" style="height:21px;">Vecta-Shield</td>
			<td>Vector Laboratories</td>
			<td>H-1000</td>
			<td></td>
		</tr>
		<tr height="21">
			<td height="21" style="height:21px;">YOPRO1</td>
			<td>Thermofisher Scientific</td>
			<td>Y3603</td>
			<td></td>
		</tr>
		<tr height="21">
			<td height="21" style="height:21px;">confocal laser scanning microscope&#160;</td>
			<td>LSM 780&#160;</td>
			<td>Zeiss</td>
			<td></td>
		</tr>
		<tr height="21">
			<td height="21" style="height:21px;">confocal laser scanning microscope&#160;</td>
			<td>LSM 700&#160;</td>
			<td>Zeiss</td>
			<td></td>
		</tr>
		<tr height="21">
			<td height="21" style="height:21px;">ImageJ software</td>
			<td colspan="2">rsb.info. nih.gov/ij/download.html&#160;</td>
			<td>free resource</td>
		</tr>
		<tr height="21">
			<td height="21" style="height:21px;">mouse anti-alpha-tubulin&#160;</td>
			<td>Sigma-Aldrich</td>
			<td>T8203</td>
			<td></td>
		</tr>
		<tr height="21">
			<td height="21" style="height:21px;">rabbit anti-acH4K16</td>
			<td>Upstate Biotechnology</td>
			<td>07-329</td>
			<td></td>
		</tr>
		<tr height="21">
			<td height="21" style="height:21px;">AlexaFluor 488-coniugated donkey anti-mouse IgG</td>
			<td>Life Technologies</td>
			<td>A21202</td>
			<td></td>
		</tr>
		<tr height="21">
			<td height="21" style="height:21px;">4&#8217;,6-diamidino-2-phenylindole&#160;</td>
			<td>Sigma-Aldrich</td>
			<td>D8417</td>
			<td>DAPI</td>
		</tr>
		<tr height="21">
			<td height="21" style="height:21px;">centrifuge</td>
			<td>Eppendorf</td>
			<td>5417R</td>
			<td></td>
		</tr>
		<tr height="21">
			<td height="21" style="height:21px;">RNALater</td>
			<td>Invitrogen</td>
			<td>AM7020</td>
			<td></td>
		</tr>
		<tr height="21">
			<td height="21" style="height:21px;">Luciferase RNA</td>
			<td>Promega</td>
			<td>L4561</td>
			<td></td>
		</tr>
		<tr height="21">
			<td height="21" style="height:21px;">PicoPure RNA Isolation Kit&#160;</td>
			<td>Applied Biosystems</td>
			<td>12204-01</td>
			<td></td>
		</tr>
		<tr height="21">
			<td height="21" style="height:21px;">random hexamers&#160;</td>
			<td>Thermofisher Scientific</td>
			<td>N8080127</td>
			<td></td>
		</tr>
		<tr height="21">
			<td height="21" style="height:21px;">mouse Moloney leukaemia virus reverse transcriptase</td>
			<td>Thermofisher Scientific</td>
			<td>28025013</td>
			<td></td>
		</tr>
		<tr height="21">
			<td height="21" style="height:21px;">SYBR green supermix&#160;</td>
			<td>BioRad</td>
			<td>1708880</td>
			<td></td>
		</tr>
		<tr height="21">
			<td height="21" style="height:21px;">specific primers</td>
			<td>Sigma-Aldrich</td>
			<td></td>
			<td>specific primers were designed using Primer3Plus software (free resource)</td>
		</tr>
		<tr height="21">
			<td height="21" style="height:21px;">thermal-cycler&#160;</td>
			<td>BioRad</td>
			<td>MyiQ&#160;</td>
			<td></td>
		</tr>
		<tr height="21">
			<td height="21" style="height:21px;">mouse monoclonal anti-CENPA</td>
			<td>Abcam</td>
			<td>ab13939</td>
			<td></td>
		</tr>
		<tr height="21">
			<td height="21" style="height:21px;">mouse monoclonal anti-Aurora B</td>
			<td>Abcam</td>
			<td>ab3609</td>
			<td></td>
		</tr>
	</tbody>
</table>

analysis of chromosome segregation, histone acetylation, and spindle morphology in horse oocytes

The field of assisted reproduction has been developed to treat infertility in women, companion animals, and endangered species. In the horse, assisted reproduction also allows for the production of embryos from high performers without interrupting their sports career and contributes to an increase in the number of foals from mares of high genetic value. The present manuscript describes the procedures used for collecting immature and mature oocytes from horse ovaries using ovum pick-up (OPU). These oocytes were then used to investigate the incidence of aneuploidy by adapting a protocol previously developed in mice. Specifically, the chromosomes and the centromeres of metaphase II (MII) oocytes were fluorescently labeled and counted on sequential focal plans after confocal laser microscope scanning. This analysis revealed a higher incidence in the aneuploidy rate when immature oocytes were collected from the follicles and matured in vitro compared to in vivo. Immunostaining for tubulin and the acetylated form of histone four at specific lysine residues also revealed differences in the morphology of the meiotic spindle and in the global pattern of histone acetylation. Finally, the expression of mRNAs coding for histone deacetylases (HDACs) and acetyl-transferases (HATs) was investigated by reverse transcription and quantitative-PCR (q-PCR). No differences in the relative expression of transcripts were observed between in vitro and in vivo matured oocytes. In agreement with a general silencing of the transcriptional activity during oocyte maturation, the analysis of the total transcript amount can only reveal mRNA stability or degradation. Therefore, these findings indicate that other translational and post-translational regulations might be affected.
Overall, the present study describes an experimental approach to morphologically and biochemically characterize the horse oocyte, a cell type that is extremely challenging to study due to low sample availability. However, it can expand our knowledge on the reproductive biology and infertility in monovulatory species.

The original findings of these experiments were described in depth previously7 and are reported herein as an example of results that can be obtained using the described protocols.
Maturation rate
Of the 32 COCs retrieved by OPU from dominant follicles, 28 (88%) were at the MII stage. Fourteen of the 58 COCs collected from follicles 5-25 mm in size ...

Watch this Scientific Journal Video about Analysis of Chromosome Segregation, Histone Acetylation, and Spindle Morphology in Horse Oocytes at JoVE.com

Analysis of Chromosome Segregation, Histone Acetylation, and Spindle Morphology in Horse Oocytes

This manuscript describes an experimental approach to morphologically and biochemically characterize horse oocytes. Specifically, the present work illustrates how to collect immature and mature horse oocytes by ultrasound-guided ovum pick-up (OPU) and how to investigate chromosome segregation, spindle morphology, global histone acetylation, and mRNA expression.

The field of assisted reproduction has been developed to treat infertility in women, companion animals, and endangered species. In the horse, assisted ...

The overall goals of this experimental approach are to, first, morphologically and biochemically characterize horse oocytes and, second, to compare gametes from the same animal that were processed in vitro or in vivo. This experimental approach can help answer key questions in oocyte biology and fertility in monovulatory species. It might also improve the safety of gamete manipulation procedures.This approach was developed to overcome the restricted sample availability of oocytes, especially from monovulatory species. Demonstrating the OPU procedures will be Professor Stefan Deleuze of the University of Liege, Cecile Douet, the lab manager of my lab, and Fabrice Reigner, the manager of the equine unit at the INRA Centre Val de Loire. On a daily basis, assess the diameter of the ovarian follicles in a cohort of adult mares using ultrasound.Search for a large follicle with a diameter greater than 33 millimeters. Once found, prepare to inject 1, 500 units of human chorionic gonadotropin to induce the maturation of the oocyte into a dominant follicle. Next, locate the jugular furrow, and swab the injection site with alcohol.Then, to make the vein rise, apply some force two or three centimeters below the site of injection. Insert the needle almost parallel to the neck, aspirate slightly to ensure that the needle is in the vein, and inject the hormone. Prepare an ultrasound probe for vaginal access.Then, connect the needle to a suction system. 35 hours after hCG injection, set up the instrumentation for OPU, and sedate the mare. Good analgesia is extremely important for the animal's and the operator's safety.An animal that does not feel pain or discomfort will allow manipulation of the ovary, making punctures and flushes easier to perform. Once the needle probe is inserted, one operator must manipulate the ovary to face the probe while the other operator manipulates the needle. Locate the dominant follicle in the echographic image.Then, use the needle to pierce the vaginal wall and the wall of the dominant follicle. Once the follicle space is accessed, aspirate the follicular fluid. Rotate the needle to scrape the follicular wall and attach the cumulus-oocyte complex.Then, pour the fluid into a large petri dish. And under a stereoscope, search for the COC. Meanwhile, flush out the follicle with warm Dulbecco's modified PBS containing heparin.It may take several flushes to collect the COC. After the COC is found, change the needle to a double-lumen needle and collect the immature COCs from all of the follicles that are between five and 25 millimeters in diameter. These will be used for in vitro maturation.Once all of the follicles from one ovary are aspirated, repeat the same procedures to collect the immature COCs from the other ovary. Now, choose between the COCs. Keep only COCs with several complete layers of cumulus cells and a brown, finely-granulated ooplasm.Discard the others. At the end of the procedure, inject the mare with 15, 000 units of benzyl-penicillin to prevent infection. Then, house the mare in a quiet, clean stable for at least two hours while she recovers.Before the OPU starts, warm a bottle of supplemented HEPES-buffered TCM-199 to 37 degrees Celsius. Next, prepare the IVM medium. Dispense 500 microliters of supplemented sodium bicarbonate-buffered TCM-199 into the wells of a four-well dish.Then, incubate the dish at 38.5 degrees Celsius for at least two hours. Transfer the recovered immature COCs to a 3.5-centimeter dish filled with two milliliters of the warmed HEPES TCM-199. Move the COCs through different regions of the dish to gently wash away surrounding debris.Now, transfer the COCs to the IVM medium, and incubate them for 28 hours at 38.5 degrees Celsius. To perform a chromosome count on mature COCs, incubate them in 100-micromolar monastrol for an hour at 38.5 degrees Celsius. Next, remove the cumulus cells by treating the COCs with 0.5%hyaluronidase in HEPES-buffered TCM-199.Monitor this reaction on a heated stage set to 38 degrees Celsius. Within about five minutes, remove all of the cells. Use gentle pipetting to remove the last few stubborn cells.Next, remove the zona pellucida using 0.2%pronase in HEPES-buffered TCM-199. Monitor this reaction on a heated stage as well. It should take about five minutes to complete.Then, fix the oocytes in 4%paraformaldehyde in DPBS for 15 minutes at 38.5 degrees Celsius, followed by 45 more minutes of fixation at four degrees Celsius. After the fixation, wash the oocytes by sequentially transferring them between three wells of 0.1%polyvinyl alcohol in DPBS. Use about half a milliliter of solution per well.Then, transfer the oocytes to a well filled with 0.3%Triton X-100 in PBS, and let them incubate for 10 minutes at room temperature. To block non-specific signals, bathe the cells in DPBS with 1%BSA and 10%normal donkey serum. Incubate the cells for at least 30 minutes at room temperature.After 30 minutes, apply the primary antibody, and then incubate the cells at four degrees Celsius overnight. The following day, wash the oocytes, and apply the secondary antibody for an hour at room temperature, shielded from light exposure. After applying the secondary, wash the oocytes again.Then, before mounting, attach double-sided tape strips to slides to serve as coverslip supports. Now, mount the oocytes three to four per slide in a drop of non-hardening, antifade mounting medium supplemented with 20 micromolar of YO-PRO-1. Allow the oocytes to settle for about 10 minutes, and then apply the coverslips.Out of 32 COCs retrieved by OPU from dominant follicles, 28 were in metaphase II.Using in vitro maturation, 37 of 44 COCs collected from non-dominant follicles were matured to metaphase II.The chromosomes of both groups were then compared. The in vitro-matured oocytes were often affected by aneuploidy, mostly hyperploidy. This was not observed in the in vivo-matured oocytes.Next, the pole-to-pole spindle length and the diameter of the spindle at its maximum were both measured. The in vitro-matured oocytes were significantly longer and wider than the in vivo-matured oocytes. In the same samples, the global acetylation level of H4K16 was measured.The results were as expected. Acetylation of H4K16 was significantly lower in in vitro-matured oocytes than in in vivo-matured oocytes. A well-trained team can process five mares in a morning of OPU with an 80%retrieval rate for the preovulatory oocyte and 50 to 60%retrieval of the immature oocytes.During the OPU, always monitor the ess and well-being of the animal, and be ready to provide adequate veterinary care if needed. The experimental approach can be applied to oocytes of other species as well and is especially applicable where samples availability is an issue, such as with humans. Based on our results, studies must be undertaken to better understand the culture conditions needed for proper chromosome segregation and epigenetic changes.The overarching goal is to improve in vitro maturation efficiency for both veterinary medicine and human fertility treatment.

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Expression of Fluorescent Proteins in Branchiostoma lanceolatum by mRNA Injection into Unfertilized Oocytes

We report here a robust and efficient protocol for the expression of fluorescent proteins after mRNA injection into unfertilized oocytes of the cephalochordate amphioxus, Branchiostoma lanceolatum. We use constructs for membrane and nuclear targeted mCherry and eGFP that have been modified to accommodate amphioxus codon usage and Kozak consensus sequences. We describe the type of injection needles to be used, the immobilization protocol for the unfertilized oocytes, and the overall injection set-up. This technique generates fluorescently labeled embryos, in which the dynamics of cell behaviors during early development can be analyzed using the latest in vivo imaging strategies. The development of a microinjection technique in this amphioxus species will allow live imaging analyses of cell behaviors in the embryo as well as gene-specific manipulations, including gene overexpression and knockdown. Altogether, this protocol will further consolidate the basal chordate amphioxus as an animal model for addressing questions related to the mechanisms of embryonic development and, more importantly, to their evolution.

Expression of Fluorescent Proteins in Branchiostoma lanceolatum by mRNA Injection into Unfertilized Oocytes

We report here the robust and efficient expression of fluorescent proteins after mRNA injection into unfertilized oocytes of Branchiostoma lanceolatum. The development of the microinjection technique in this basal chordate will pave the way for far-reaching technical innovations in this emerging model system, including in vivo imaging and gene-specific manipulations.

We report here a robust and efficient protocol for the expression of fluorescent proteins after mRNA injection into unfertilized oocytes of the ...

Analysis of Zebrafish Larvae Skeletal Muscle Integrity with Evans Blue Dye

The zebrafish model is an emerging system for the study of neuromuscular disorders. In the study of neuromuscular diseases, the integrity of the muscle membrane is a critical disease determinant. To date, numerous neuromuscular conditions display degenerating muscle fibers with abnormal membrane integrity; this is most commonly observed in muscular dystrophies. Evans Blue Dye (EBD) is a vital, cell permeable dye that is rapidly taken into degenerating, damaged, or apoptotic cells; in contrast, it is not taken up by cells with an intact membrane. EBD injection is commonly employed to ascertain muscle integrity in mouse models of neuromuscular diseases. However, such EBD experiments require muscle dissection and/or sectioning prior to analysis. In contrast, EBD uptake in zebrafish is visualized in live, intact preparations. Here, we demonstrate a simple and straightforward methodology for performing EBD injections and analysis in live zebrafish. In addition, we demonstrate a co-injection strategy to increase efficacy of EBD analysis. Overall, this video article provides an outline to perform EBD injection and characterization in zebrafish models of neuromuscular disease.

In this study, we describe a straightforward method to perform Evans Blue Dye (EBD) analysis on zebrafish larvae. This technique is a powerful tool for the characterization of skeletal muscle integrity and delineation of zebrafish models of muscular dystrophy, and is a valuable method for the development of novel therapeutics.

The zebrafish model is an emerging system for the study of neuromuscular disorders.  In the study of neuromuscular diseases, the integrity of the muscle ...

Isolation and Characterization of Mouse Antral Oocytes Based on Nucleolar Chromatin Organization

This protocol describes a simple and quick method to isolate and characterize mouse antral GV (Germinal Vesicle) oocytes as able (SN, Surrounded Nucleolus) or unable (NSN, Not Surrounded Nucleolus) to develop to the blastocyst stage after in vitro maturation (IVM) and in vitro fertilization (IVF). It makes use of Hoeschst33342 (or any other DNA intercalating dye) able to bind to the heterochromatin of the nucleolus showing a ring in the SN oocytes or not, like in the NSN oocytes. This represents the easiest and quickest way to sort both antral oocytes that can be eventually used for IVM or IVF procedures. 
Briefly, the protocol consists of the following steps: hormone injection to stimulate follicular growth; isolation of the oocytes at the GV stage from the antral compartment by puncturing the ovary with a sterile needle; preparation of thin glass pipettes for mouth pipetting of the oocytes; sorting of the oocytes with Hoechst33342 prepared at a supravital concentration; IVM, IVF or any other molecular/cellular analysis.
Unfortunately there are still few evidences to sort SN and NSN oocytes using less invasive techniques. If and once they will be identified, they could be potentially applied to human assisted reproductive technologies, although with several aspects that should be modified. To date, this technique has potential implications to dramatically increase IVM and IVF successful procedures in both endangered and species with economic interest.

Here we present a protocol for the characterization of mouse antral oocytes based on nucleolar organization.

This protocol describes a simple and quick method to isolate and characterize mouse antral GV (Germinal Vesicle) oocytes as able (SN, Surrounded ...

Spatial and Temporal Analysis of Active ERK in the C. elegans Germline

The evolutionarily conserved&#160;extracellular signal transducing RTK-RAS-ERK pathway is an important kinase-signaling cascade that controls multiple cellular and developmental processes principally via activation of ERK, the terminal kinase of the pathway. Tight regulation of ERK activity is essential for normal development and homeostasis; overly active ERK results in excessive cellular proliferation, while underactive ERK causes cell death. C. elegans is a powerful model system that has helped characterize the function and regulation of RTK-RAS-ERK signaling pathway during development. In particular, the RTK-RAS-ERK pathway is essential for C. elegans germline development, which is the focus of this method. Using antibodies specific to the active, diphosphorylated form of ERK (dpERK), the stereotypical localization pattern can be visualized within the germline. Because this pattern is both spatially and temporally controlled, the ability to reproducibly assay dpERK is useful to identify regulators of the pathway that affect dpERK signal duration and amplitude and thus germline development. Here we demonstrate how to successfully dissect, stain, and image dpERK within the C. elegans gonad. This method can be adapted for spatial localization of any signaling or structural protein in the C. elegans gonad, provided an antibody compatible with immunofluorescence is available.

Spatial and Temporal Analysis of Active ERK in the C. elegans Germline

We present an immunofluorescence&#160;imaging-based method for spatial and temporal localization of active ERK in the dissected C. elegans gonad. The protocol described here can be adapted for visualization of any signaling or structural protein in the C. elegans gonad, provided a suitable antibody reagent is available.

The evolutionarily conserved&#160;extracellular signal transducing RTK-RAS-ERK pathway is an important kinase-signaling cascade that controls multiple ...

Generation of Genetically Modified Mice through the Microinjection of Oocytes

The use of genetically modified mice has significantly contributed to studies on both physiological and pathological in vivo processes. The pronuclear injection of DNA expression constructs into fertilized oocytes remains the most commonly used technique to generate transgenic mice for overexpression. With the introduction of CRISPR technology for gene targeting, pronuclear injection into fertilized oocytes has been extended to the generation of both knockout and knockin mice. This work describes the preparation of DNA for injection and the generation of CRISPR guides for gene targeting, with a particular emphasis on quality control. The genotyping procedures required for the identification of potential founders are critical. Innovative genotyping strategies that take advantage of the "multiplexing" capabilities of CRISPR are presented herein. Surgical procedures are also outlined. Together, the steps of the protocol will allow for the generation of genetically modified mice and for the subsequent establishment of mouse colonies for a plethora of research fields, including immunology, neuroscience, cancer, physiology, development, and others.

The microinjection of mouse oocytes is commonly used for both classic transgenesis (i.e., the random integration of transgenes) and CRISPR-mediated gene targeting. This protocol reviews the latest developments in microinjection, with a particular emphasis on quality control and genotyping strategies.

The use of genetically modified mice has significantly contributed to studies on both physiological and pathological in vivo processes. The pronuclear ...

Live Cell Imaging of Chromosome Segregation During Mitosis

Chromosomes must be reliably and uniformly segregated into daughter cells during mitotic cell division. Fidelity of chromosomal segregation is controlled by multiple mechanisms that include the Spindle Assembly Checkpoint (SAC). The SAC is part of a complex feedback system that is responsible for prevention of a cell progress through mitosis unless all chromosomal kinetochores have attached to spindle microtubules. Chromosomal lagging and abnormal chromosome segregation is an indicator of dysfunctional cell cycle control checkpoints and can be used to measure the genomic stability of dividing cells. Deregulation of the SAC can result in the transformation of a normal cell into a malignant cell through the accumulation of errors during chromosomal segregation. Implementation of the SAC and the formation of the kinetochore complex are tightly regulated by interactions between kinases and phosphatase such as Protein Phosphatase 2A (PP2A). This protocol describes live cell imaging of lagging chromosomes in mouse embryonic fibroblasts isolated from mice that had a knockout of the PP2A-B56&#947; regulatory subunit. This method overcomes the shortcomings of other cell cycle control imaging techniques such as flow cytometry or immunocytochemistry that only provide a snapshot of a cell cytokinesis status, instead of a dynamic spatiotemporal visualization of chromosomes during mitosis.

This protocol describes an easy and convenient method to label and visualize live chromosomes in mitotic cells using Histone2B-GFP BacMam 2.0 label and a spinning disc confocal microscopy system.

Chromosomes must be reliably and uniformly segregated into daughter cells during mitotic cell division. Fidelity of chromosomal segregation is controlled ...

Minimum Volume Vitrification of Immature Feline Oocytes

In wild animals&#8217; conservation programs, gamete banking is crucial to safeguard genetic resources of valuable individuals and rare species and to promote biodiversity preservation. In felids, most species are threatened with extinction, and domestic breeds are used as a model to increase the efficiency of protocols for germplasm banking. Among oocyte cryopreservation techniques, vitrification is more and more popular in human and veterinary assisted reproduction. Cryotop vitrification, which was at first developed for human oocytes and embryos, has demonstrated to be well-suited for cat oocytes. This method offers several advantages, such as the feasibility in field conditions and the speed of the procedure, which can be helpful when several samples need to be processed. However, the efficiency is strongly dependent on the operator&#8217;s skills, and intra- and inter-laboratory standardization are needed, as well as personnel training. This protocol describes minimum volume vitrification of immature feline oocytes on a commercial support in a step by step field-friendly protocol, from oocyte collection to warming. Following the protocol, preservation of oocyte integrity and viability at warming (as high as 90%) can be expected, although there is still room for improvement in post-warming maturation and embryonic development outcomes.

This manuscript describes a protocol for the minimum volume vitrification of immature cat oocytes with laboratory-made media on commercial supports. It covers every step from oocyte isolation from ex vivo gonads to vitrification and warming.

In wild animals&#8217; conservation programs, gamete banking is crucial to safeguard genetic resources of valuable individuals and rare species and to ...

In Vitro Culture Strategy for Oocytes from Early Antral Follicle in Cattle

The limited reserve of mature, fertilizable oocytes represents a major barrier for the success of assisted reproduction in mammals. Considering that during the reproductive life span only about 1% of the oocytes in an ovary mature and ovulate, several techniques have been developed to increase the exploitation of the ovarian reserve to the growing population of non-ovulatory follicles. Such technologies have allowed interventions of fertility preservation, selection programs in livestock, and conservation of endangered species. However, the vast potential of the ovarian reserve is still largely unexploited. In cows, for instance, some attempts have been made to support in vitro culture of oocytes at specific developmental stages, but efficient and reliable protocols have not yet been developed. Here we describe a culture system that reproduce the physiological conditions of the corresponding follicular stage, defined to develop in vitro growing oocytes collected from bovine early antral follicles to the fully-grown stage, corresponding to the medium antral follicle in vivo. A combination of hormones and a phosphodiesterase 3 inhibitor was used to prevent untimely meiotic resumption and to guide oocyte&#39;s differentiation.

We describe the procedures for isolation of growing oocytes from ovarian follicles at early stages of development, as well as the setup of an in vitro culture system which can support the growth and differentiation up to the fully-grown stage. &#160;

The limited reserve of mature, fertilizable oocytes represents a major barrier for the success of assisted reproduction in mammals. Considering that ...

Separation of Follicular Cells and Oocytes in Ovarian Follicles of Zebrafish

Zebrafish has become an ideal model to study the ovarian development of vertebrates. The follicle is the basic unit of the ovary, which consists of oocytes and surrounding follicular cells. It is vital to separate both follicular cells and oocytes for various research purposes such as for primary culture of follicular cells, analysis of gene expression, oocyte maturation and in vitro fertilization, etc. The conventional method uses forceps to separate both compartments, which is laborious, time consuming and has high damage to the oocyte. Here, we have established a simple method to separate both compartments using a pulled glass capillary. Under a stereomicroscope, oocytes and follicular cells can be easily separated by pipetting in a pulled fine glass capillary (the diameter depends on the follicle diameter). Compared with the conventional method, this new method has high efficiency in separating both oocytes and follicular cells and has low damage to the oocytes. More importantly, this method can be applied to early-stage follicles including at the pre-vitellogenesis stage. Thus, this simple method can be used to separate follicular cells and oocytes of zebrafish.

Here, we present a simple method for separating follicular cells and oocytes in zebrafish ovarian follicles, which will facilitate investigations of ovarian development in zebrafish.

Zebrafish has become an ideal model to study the ovarian development of vertebrates. The follicle is the basic unit of the ovary, which consists of ...

Vitrification of In Vitro Matured Oocytes Collected from Adult and Prepubertal Ovaries in Sheep

In livestock, in vitro embryo production systems can be developed and sustained thanks to the large number of ovaries and oocytes that can be easily obtained from a slaughterhouse. Adult ovaries always bear several antral follicles, while in pre-pubertal donors the maximal numbers of oocytes are available at 4 weeks of age, when ovaries bear peak numbers of antral follicles. Thus, 4 weeks old lambs are considered good donors, even if the developmental competence of prepubertal oocytes is lower compared to their adult counterpart. 
Basic research and commercial applications would be boosted by the possibility of successfully cryopreserving vitrified oocytes obtained from both adult and prepubertal donors. The vitrification of oocyte collected from prepubertal donors would also allow shortening the generation interval and thus increasing the genetic gain in breeding programs. However, the loss of developmental potential after cryopreservation makes mammalian oocytes probably one of the most difficult cell types to cryopreserve. Among the available cryopreservation techniques, vitrification is widely applied to animal and human oocytes. Despite recent advancements in the technique, exposures to high concentrations of cryoprotective agents as well as chilling injury and osmotic stress still induce several structural and molecular alterations and reduce the developmental potential of mammalian oocytes. Here, we describe a protocol for the vitrification of sheep oocytes collected from juvenile and adult donors and matured in vitro prior to cryopreservation. The protocol includes all the procedures from oocyte in vitro maturation to vitrification, warming and post-warming incubation period. Oocytes vitrified at the MII stage can indeed be fertilized following warming, but they need extra time prior to fertilization to restore damage due to cryopreservation procedures and to increase their developmental potential. Thus, post-warming culture conditions and timing are crucial steps for the restoration of oocyte developmental potential, especially when oocyte are collected from juvenile donors.

The protocol aims at providing a standard method for the vitrification of adult and juvenile sheep oocytes. It includes all the steps from the preparation of the in vitro maturation media to the post-warming culture. Oocytes are vitrified at the MII stage using Cryotop to ensure the minimum essential volume.

In livestock, in vitro embryo production systems can be developed and sustained thanks to the large number of ovaries and oocytes that can be easily ...